SplittableRandom

A generator of uniform pseudorandom values applicable for use in
(among other contexts) isolated parallel computations that may
generate subtasks. Class SplittableRandom supports methods for
producing pseudorandom numbers of type int, long,
and double with similar usages as for class
Random but differs in the following ways:

Series of generated values pass the DieHarder suite testing
independence and uniformity properties of random number generators.
(Most recently validated with version
3.31.1.) These tests validate only the methods for certain
types and ranges, but similar properties are expected to hold, at
least approximately, for others as well. The period
(length of any series of generated values before it repeats) is at
least 264.

Method split() constructs and returns a new
SplittableRandom instance that shares no mutable state with the
current instance. However, with very high probability, the
values collectively generated by the two objects have the same
statistical properties as if the same quantity of values were
generated by a single thread using a single SplittableRandom object.

Instances of SplittableRandom are not thread-safe.
They are designed to be split, not shared, across threads. For
example, a fork/join-style computation using random numbers might include a
construction of the form new
Subtask(aSplittableRandom.split()).fork().

This class provides additional methods for generating random
streams, that employ the above techniques when used in stream.parallel() mode.

Instances of SplittableRandom are not cryptographically
secure. Consider instead using SecureRandom
in security-sensitive applications. Additionally,
default-constructed instances do not use a cryptographically random
seed unless the system propertyjava.util.secureRandomSeed is set to true.

Summary

Public constructors

Creates a new SplittableRandom instance that is likely to
generate sequences of values that are statistically independent
of those of any other instances in the current program; and
may, and typically does, vary across program invocations.

Returns a stream producing the given streamSize number of
pseudorandom double values from this generator and/or one split
from it; each value conforms to the given origin (inclusive) and bound
(exclusive).

Returns a stream producing the given streamSize number
of pseudorandom int values from this generator and/or one split
from it; each value conforms to the given origin (inclusive) and bound
(exclusive).

longs(long streamSize, long randomNumberOrigin, long randomNumberBound)

Returns a stream producing the given streamSize number of
pseudorandom long values from this generator and/or one split
from it; each value conforms to the given origin (inclusive) and bound
(exclusive).

Causes the current thread to wait until another thread invokes the
notify() method or the
notifyAll() method for this object, or
some other thread interrupts the current thread, or a certain
amount of real time has elapsed.

SplittableRandom

Creates a new SplittableRandom instance that is likely to
generate sequences of values that are statistically independent
of those of any other instances in the current program; and
may, and typically does, vary across program invocations.

doubles

Returns a stream producing the given streamSize number of
pseudorandom double values from this generator and/or one split
from it; each value conforms to the given origin (inclusive) and bound
(exclusive).

ints

Returns a stream producing the given streamSize number
of pseudorandom int values from this generator and/or one split
from it; each value conforms to the given origin (inclusive) and bound
(exclusive).

longs

Returns a stream producing the given streamSize number of
pseudorandom long values from this generator and/or one split
from it; each value conforms to the given origin (inclusive) and bound
(exclusive).

split

Constructs and returns a new SplittableRandom instance that
shares no mutable state with this instance. However, with very
high probability, the set of values collectively generated by
the two objects has the same statistical properties as if the
same quantity of values were generated by a single thread using
a single SplittableRandom object. Either or both of the two
objects may be further split using the split() method,
and the same expected statistical properties apply to the
entire set of generators constructed by such recursive
splitting.